This invention relates generally to a solid state laser, and more particularly relates to a solid state laser resonator.
The advantage of a conventional solid state laser excited by imparting a laser light to an end face or end faces thereof is that it easily obtains the TEM.sub.oo mode as compared with a conventional solid state laser excited by imparting a pumping light to a side or sides thereof. However, in operation, it is difficult for the former to impart a laser light for producing a high-power output laser light.
A tandem solid state laser resonator excited by laser lights 1, 2 in a multistage manner as shown in FIG. 10 and a solid state laser resonator as shown in FIG. 11 excited by imparting laser lights to multiside thereof are developed to obtain a high-power output laser light having the advantage of the former.
The solid state laser resonator of FIG. 10 is designed to impart the laser lights 1,2, generated from laser generators to laser rods 3,4, respectively, and to be resonated by mirrors 5,6 and an output mirror 7 so as to obtain an output laser light 8.
The solid state laser resonator of FIG. 11 is designed to impart the laser lights through optical fibers 12 to a Nd: YAG (Yttrium-aluminium-garnet) crystal. In FIG. 11, reference numeral 13 indicates an output mirror and a reference numeral 14 indicates a semiconductor laser.
Since the optical system of the solid state laser resonator of FIG. 10 requires many components including the mirrors 5,6 and 7, the optical system is large to arrange the components in their necessary position. Also, in FIG. 10, since the mirrors 5,6 are arranged between the end faces of the rods 3,4 for imparting the laser lights thereto, the distance from each of the laser generators to the end face of the rod is great for focusing (to pump). Thus it is impossible to inexpensively design the optical system for the laser resonator.
The optical system of the solid state laser resonator of FIG. 11 is provided to solve the above-mentioned problems of the optical system of FIG. 10. However, although the optical system of FIG. 11 requires a large homogeneous Nd: YAG crystal 11, which is difficult to make or obtain the large homogeneous Nd: YAG crystal 11 and thus the production or acquisition cost thereof is high.
Furthermore, in the case of a solid state laser pumped by imparting a laser light or laser lights from a semiconductor laser or semiconductor lasers to an end face or end faces thereof, as the laser beam diameter of the laser light is very small compared with the size of a crystal, the crystal is utilized for imparting the laser light thereto in a very inefficient manner.
In a further conventional solid state laser, a slab crystal is excited to produce an output laser power in a highly efficient manner. However, the slab crystal which is formed in a rectangular plate has an effective oscillation volume greater than that of a rod-shaped crystal.
Recently, to provide a semiconductor laser which can generate a high-power laser output light, the solid state laser of FIG. 11 is used for the high-power semiconductor laser or laser as a pumping source.
However, in the conventional solid state laser including the slab crystal or the solid state laser of FIG. 11, an optical path runs zigzag in the laser base material such as the Nd: YAG crystal 11. In the conventional solid state laser of FIG. 11, light from the semiconductor laser 14, for pumping a laser light along a zigzag optical path, is imparted along a direction different than the zigzag optical path.
Also, for example, the zigzag optical path has at least two different directions in the laser base material arranged in such a manner that one of the two different directions coincides with the crystal orientation for generating the laser light while the other of the two different directions does not coincide with the crystal orientation. Thus, the other of the two different directions has no relation to the laser oscillating operation. A characteristic, such as a polarization characteristic, almost prevents the laser oscillating operation.